JPS6128381B2 - - Google Patents

Abstract

A circuit for applying unidirectional pulses to a precipitator, in addition to a base d.c. level supplied by a transformer/rectifier set, includes a rectifier, an inverter and a transformer/rectifier set connected to charge a storage capacitor. Discharge of the capacitor into the precipitator is controlled by a chain of unidirectionally conducting devices (thyristors as shown) which are simultaneously triggered at the desired voltage at the capacitor. In other embodiments breakover diodes are used instead of the thyristors.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for supplying voltage pulses to an electrostatic precipitator, where the pulses are superimposed on an independently supplied base voltage level.

It has proven advantageous to provide electrostatic precipitators with high voltage pulses in addition to the substantially constant voltage provided by conventional and known means for treating certain types of dust.

It is an object of the invention to provide an electrostatic precipitator with a circuit for providing voltage pulses of this type.

The present invention is a circuit for supplying voltage pulses to an electrostatic precipitator, the circuit comprising a storage capacitor, means for charging the storage capacitor to a desired pulsed voltage, and coupled to the storage capacitor for coupling to the precipitator. unidirectional conduction means for connecting the capacitor to the precipitator; and control means for energizing the unidirectional conduction means to connect the capacitor to the precipitator.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings.

In FIG. 1, an electrostatic precipitator 10 is supplied with a DC base voltage level by a conventional transformer and rectifier set, the voltage level being controlled at 12 as required. Furthermore, the rectifier is supplied with voltage pulses on line 14 from a thyristor switch 15, which is also supplied from mains 17 through a cascaded AC/DC converter 18, an inverter 19 and a set of transformer rectifiers 20. The thyristor switch 15 is triggered by a control circuit 22 having a control input 23. The frequency of the signal at input 23 determines the frequency of the voltage pulses on line 14, while the amplitude of the pulses is determined at input 25 to AC/DC converter 18.

2, converter 18 is in the form of a simple bridge rectifier, which supplies power through coil 28 to inverter 19. The two rectifiers 26 filling the positive output line 27 of the bridge are controlled rectifiers whose gates are supplied with the signal 25.

The inverter 19 includes two capacitors 30 and 31 connected in series between the positive and negative lines 27 and 29, two resistors 32 and 33 also connected in series, and the set 20.
Thyristors 41 and 42 connect respective lines 27 and 29 to the ends of primary windings 35 and 36 of the transformer 39, respectively.
and a capacitor 40 connecting the midpoint of the resistors 32, 33 and capacitors 30, 31 to the common point of the windings 35, 36. It should be noted that windings 35 and 36 are wound in opposite directions.

The thyristors 41 and 42 have diodes connected in opposite directions in parallel, and control the discharge voltage of the capacitor 40 via the windings 35 and 36, while the amplitude of each discharge voltage is determined by the voltage formed in the capacitors 30 and 31. . This voltage is due to the conduction time of the thyristor, which is controlled by signal 25. Therefore transformer 39
The frequency and amplitude of the high voltage pulses in the secondary winding 43 are controlled.

The secondary winding 43 of the transformer/rectifier set 20 is connected to a bridge rectifier 45, the positive terminal of which is grounded and the negative terminal connected through an inductor 46 to a chain group of unidirectional conducting devices, in this case eight thyristors. It is connected to the negative terminal of 47. The positive terminal of the chain group is connected to the negative side of the precipitator 10 via an inductor 48 and a capacitor 49 connected in series. Inductor 50 and storage capacitor 51 ground the positive and negative terminals of thyristor chain group 47. In this way, the output pulses from the bridge rectifier 45 charge the capacitor 51, which is discharged into the precipitator when the thyristor chain 47 conducts under the control of the circuit 22.

In order to prevent any of the thyristors in the chain group 47 from becoming overloaded, it is necessary to ensure that all the thyristors in the chain group are rendered conductive at the same time, and the control circuit 22 for this purpose is shown in FIG. detailed.

A signal 60 determining the firing rate of the thyristor chain 47 is fed to a voltage controlled oscillator 61 which powers a timer 62 . The timer also triggers a power switch 63 to apply a chain of eight light emitting diodes 64. Each diode is observed with an optical fiber 65, and each fiber 65 is
The light pulse passes through a splitter 66 where it is split into five paths. The five output fibers 67 each lead to a respective control circuit 68 which respectively controls the firing of the two thyristors of the chain group 47. The 40 light pulses in the fibers 67 from the eight light splitters 66 are found to be simultaneous, and one of the control circuits 68 is shown in FIG. Each control circuit controls the firing of two thyristors of chain group 47 in response to pulses of fiber 67.

In FIG. 4, an incoming fiber 67 illuminates a detector 70 which transmits the electrical signal to an amplifier 7.
1, the output of the amplifier is delayed at 72, and the output of the amplifier is delayed at 73.
and is used to trigger the VMOS power switch 74. The output of switch 74 is connected to the primary winding of a pulse transformer 75 having two secondary windings each connected to trigger one transistor of chain group 47. Amplifier 71,
Power is supplied to the delay device 72, the rectangular waveformer 73, and the switch 74 from one secondary winding 40 of the transformer 77. The delay made at 72 is adjusted to match the firing of the two thyristors with the firing of the other 78 thyristors in chain group 47.

The overall performance of the FIG. 1 circuit is controlled to provide the precipitator with pulses whose amplitude, frequency, and duration are controlled to suit the operational demands of the precipitator. Results to date have shown that the DC level provided by the transformer/rectifier set is reduced by about 10% compared to normal DC operation and doubled at a frequency of about 50 pulses/second for a duration of about 100 μs. It has been suggested that optimal results are achieved using pulses with an amplitude equal to the magnitude of .

Fig. 5 shows a modified example, and here the first
The thyristor switch 15 in the figure is replaced by a chain group of breakover diodes with a fixed breakover voltage of, for example, 1000V, the other characteristics of the diodes being the same as those of the thyristor.

The output of the transformer/rectifier set 20 is connected to a storage capacitor 51 via an inductor, a chain group 80 of more than 80 capacitors each having a resistor connected in parallel, and a chain group 80 each having a resistor and a diode connected in parallel for overvoltage protection. The chain group 81 of breakover diodes and the precipitator 10 itself are energized. Assuming that the circuit remains inoperable until the capacitor 51 is charged above approximately 80 KV, the diode chain 82 is connected in series with the secondary winding 83 of the transformer 84, with each diode having a parallel resistance. A control circuit is also provided. The primary winding 85 of the transformer 84 is energized at the desired frequency by a thyristor circuit switch 86. Diode chain 80 is adapted to isolate capacitor 50 from the anode of chain 82. In this way, the positive end of diode chain 82 is driven negative with each pulse, making the chain conductive, and a negative pulse is added to the positive end of breakover diode chain 81, which in turn causes chain 81 to conduct. and connect the capacitor 51 to the dust collector 10. The pulse frequency in precipitator 10 is controlled by the frequency of the control pulse to switch 86.

In the modification of FIG. 5, the breakover diode circuit is modified as shown in FIG. Only one breakover diode 81 is shown. It will be appreciated that circuitry is provided to trigger conduction of diode 81. Fifth
The main change in Figure 6 compared to the figure is the inductor 5 in Figure 5.
0 is replaced by a parallel combination of a resistor 90 and a diode 91 with the anode grounded. Also, the breakover diode is a reversely connected diode 9.
In addition to the resistor 93 and the resistor 93, a series-connected combination of a resistor 94 and a capacitor 95 is also connected in parallel.

The operation of FIG. 6 is as follows. First, capacitor 51 is charged through ground by transformer rectifier set 20. When the breakover diode conducts, capacitor 51 discharges providing the desired negative pulse to the precipitator. It is understood that the resistance value of the resistor 90 is sufficiently large that the discharge of the capacitor 51 is not short-circuited by the resistor 90.

When the precipitator is implemented, the capacitor is charged, and the ground, capacitor 51, diode 92,
It discharges through a circuit having an inductor 48 and a capacitor 49, returning the reduced energy broadly to the capacitor 51. Diode 91 acts to clamp the negative terminal of capacitor 50 during the release of the inductive energy stored in inductor 48 . Capacitor 95 and resistor 94 function to abruptly stop and control the rate of voltage change across the inductor.

In a variation of the example of FIG. 6, the high power level is adjusted using a breakover diode in the gate circuit of the thyristor to control the firing of the thyristor, a variation of which is shown in FIG. Each breakover diode 81 (and its associated diode and resistor) in FIG.
01. On the other hand, this gate is connected to the anode by a resistor 104 and a Zener diode 105 connected in parallel.

Although the described embodiment assumes having separate supplies for the base DC level and the pulses, a transformer/rectifier set providing the base DC level to energize the thyristor switch 15 of FIG. This can also be accomplished by using a breakover diode chain as shown in FIG.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram of a first example of a power supply system for an electrostatic precipitator according to the present invention, Fig. 2 is a detailed circuit diagram of the example shown in Fig. 1, and Fig. 3 is a detail of a part of Fig. 2. figure,
4 is a more detailed diagram of a part of FIG. 3, FIG. 5 is a detailed circuit diagram of a part of the second embodiment of the present invention, and FIG.
The figure shows a circuit diagram of a modification of FIG. 5, and FIG. 7 shows a further modification of the example of FIG. 6. 10: Precipitator, 19: Inverter, 22: Control circuit, 47: Unidirectional conduction device chain group, 51: Capacitor, 64: Light emitting diode, 65: Optical fiber, 66: Optical light Splitter, 67: Optical fiber, 68:
Firing control circuit, 81: Breakover diode chain group, 82: Diode chain group, 83: Secondary winding, 84: Transformer.

Claims (1)

[Claims] 1. A circuit for supplying voltage pulses to an electrostatic precipitator, the circuit comprising: a storage capacitor;
means for charging the storage capacitor to the pulsed voltage; a series of thyristors coupled to the capacitor and coupled to the electrostatic precipitator; control means for conducting said series of thyristors to connect said thyristors, each of said thyristors having a breakover diode connected between its cathode and its gate; , is connected to its anode through a resistor and a parallel connection of a zener diode, and its cathode is connected to its anode through a resistor and a capacitor, a reversely connected diode, and a parallel connection of a resistor. voltage pulse supply circuit. 2 A circuit for supplying voltage pulses to an electrostatic precipitator, to which a base DC voltage is independently supplied, and the voltage pulse supply circuit and a series of unidirectional conduction devices, the unidirectional conduction device comprising a series of thyristors connected in series to the electrostatic precipitator via a coupling capacitor, Each has a breakover diode connected between its cathode and its gate, whose gate is connected to its anode through a resistor and a parallel connection of zener diodes, and whose cathode is connected to its anode through a resistor and a parallel connection of zener diodes. and an impedance connected to its anode through a parallel connection of a capacitor, a reversely connected diode, and a resistor, and further connected between the series combination of the storage capacitor and the series of thyristors; a pulsed voltage supply comprising means for charging a capacitor for use to said pulsed voltage and control means for simultaneously energizing said series of thyristor devices to connect said storage capacitor to said electrostatic precipitator. circuit. 3. A circuit for supplying voltage pulses to an electrostatic precipitator, the circuit comprising: a storage capacitor; means for charging the capacitor to the pulse voltage; a series of thyristors coupled to an electrostatic precipitator; and control means for energizing the series of thyristors to connect the capacitor to the electrostatic precipitator, the control means comprising a series of lights. The light transmitting means includes an emitting diode and an optical light splitter, and includes a control circuit that simultaneously receives light pulses from the light transmitting means and simultaneously triggers the series of thyristors. A voltage pulse supply circuit including an optical fiber extending between an emitting diode and the optical light splitter and between the optical light splitter and the control circuit.